The Food and Drug Administration is cracking down on the California genetics company 23andMe. The FDA has ordered the company to stop selling tests that claim to provide people medical information by analyzing their DNA. As NPR's Rob Stein reports, the agency is concerned about the accuracy of the testing.

ROB STEIN, BYLINE: 23andMe is probably the most well-known company selling genetic tests directly to consumers. It aggressively markets its DNA tests in ads like this one.

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STEIN: Some of 23andMe's tests are just for fun.

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STEIN: No one has any problems with those tests. And the company's got lots of loyal customers who like how it champions easy access to genetic information. But 23andMe's tests claim to do a lot more than that.

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STEIN: And that's where the company is running into problems. The FDA's Courtney Lias says the agency has been trying for years to get the company to prove its tests are accurate, that they're reliable, and that people understand what they mean.

COURTNEY LIAS: And they have not been able to provide that information despite us giving them ample time to do so.

STEIN: So the FDA sent 23andMe a letter, a really toughly worded letter for the FDA, telling the company that basically time's up. Stop selling those medical tests immediately until you prove to us they're safe.

LIAS: They don't have no any way of knowing whether or not their test is as accurate as they say that it is because they haven't provided the information that either we or they would need to know how accurate the test is.

STEIN: And the FDA says the are some real dangers. One test claims to tell people whether they're taking the right dose of a powerful blood thinner.

LIAS: And if that result is incorrect and they change the dose that they're taking while they're at home, then they may be at risk for stroke or even sudden death.

STEIN: Couples who find out they're supposedly carrying a genetic disease may abort a pregnancy. Women who find out they're at risk for breast cancer may get mastectomies for no good reason.

LIAS: So if people are going to rely on the results of tests like this to make important decisions like that, we need to make sure that those tests provide accurate results.

STEIN: The FDA's decision was welcomed by experts in genetics. James Evans is a geneticist at the University of North Carolina at Chapel Hill.

JAMES EVANS: I think that it's a appropriate, sober decision. It's completely in line with the best interests of public health.

STEIN: Evans says it's one thing to offer to test people to find out where their families are from, who their parents are or whether they might have certain food preferences. But when you start offering people medical advice, you have to be careful.

23andMe declined to make anyone available for an interview. In a statement, the company said it would work with the FDA to try to answer their concerns. The FDA says the company has 15 days to respond. Rob Stein, NPR News. Transcript provided by NPR, Copyright NPR.